Using data from the 2002 National Survey of Family Growth, the report analyzed 10-year survival trajectories of marriages according to whether the partners cohabited before marrying. The overall finding was very little difference in marriage survival. However, there was a difference among cohabitors — between those who were engaged when they started living together and those who weren’t.

Seems we can’t say much about what cohabitation itself does to impact marriage survival. But the kind of commitment people make before they move in together could make a difference. So this might just be an indicator of the strength of pre-marriage commitment couples have (or something else about the nature of their relationships).

Striking as its presence has become on the demographic palette, cohabitation has been hard to study, because although it precedes more marriages, it’s a state most people don’t stay in for long, and they get into for very different reasons, in different contexts. That also means this Pew question (from the USA Today story) — about “more people living together without getting married” — is only getting at some of the phenomenon.